The present invention relates to an image composing apparatus applicable to the tracing of a bright spot within an image, the measurement of a three-dimensional curved surface shape, etc.
Included among the presently commercially available digital frame memories for image storage purposes are those having a variety of image preliminarily processing functions. One of such image preliminary processing functions is a maximum brightness image processing function or minimum brightness image processing function.
Here, the maximum brightness image processing function (or the minimum brightness image processing function) is such that using for example a circuit as shown in FIG. 1, the video signal inputted from a television camera is compared with the image stored in a frame memory so as to determine in a realtime manner the relative magnitude of the corresponding picture elements to successively update the frame memory by the greater values (or the smaller values), thereby producing a composite image in which each of the picture elements has its maximum value (or its minimum value) within a given time period of the video signal. It is to be noted that FIG. 1 of the accompanying drawings shows an example of the maximum brightness image processing circuit and the description of its details will be omitted since the substantial description will be given in connection with the later description of an embodiment of the invention.
FIG. 2 shows an example in which the locus of a bright spot 30 is determined by the use of the maximum brightness image processing function, that is, the locus of the bright spot 30 moving within an image is determined by a maximum brightness image processing circuit 3 and displayed on a monitor television 20.
On the other hand, FIGS. 3 and 4 show another example which utilizes the minimum brightness image processing function to obtain a virtual cutting image. As shown in FIG. 3, a low-magnification microscope 31 is connected to a television camera 2 and a stroboscope light source 32 is arranged opposite to the microscope 31 through a rotary tool 33 to form a silhouette image of the rotary tool 33 on a monitor television 20. Then, if, in this case, the video signal is processed by a minimum brightness image processing circuit 3a as shown in FIG. 4, a virtual cutting surface image 34 of the cutting tool edges is obtained and the virtual cutting surface of the cutting edges of the rotary tool 33 moving across the silhouette image can he observed.
As described hereinabove, each of the maximum brightness image processing function and the minimum brightness image processing function is a convenient function as image composing means for image preliminary processing purposes.
However, in the tracing of the bright spot 30 shown in FIG. 2, for example, while the locus of the spot 30 can be observed, it is impossible to measure the speeds of the spot at various points on the locus from the maximum brightness image obtained by the maximum brightness image processing function. Similarly, it is impossible to know the times of passage of the cutting edges on the virtual cutting surface image of the cutting edges of the rotary tool 33 shown in FIGS. 3 and 4.
These deficiencies are due to the fact that the maximum brightness image processing function or the minimum brightness image processing function merely serves a function of simply storing brightness information for each picture element.